15.4
병원체의 정착
병원체가 숙주 조직에 정착하는 것은 감염병 발달에 있어 중요한 단계입니다. 박테리아, 곰팡이, 바이러스, 원생동물 등 다양한 병원성 미생물은 숙주 환경에 부착, 침입, 지속하기 위한 복잡한 전략을 진화시켜 왔습니다. 이러한 기전들은 병원체가 감염을 확립하고 면역 반응을…
많은 원핵생물 및 진핵생물 병원체는 즉각적인 질병 발생 없이 숙주 조직에 정착할 수 있습니다. 감염은 집락화가 조직 손상이나 숙주 염증 반응을 초래할 때만 발생합니다.
박테리아는 숙주 세포에 부착함으로써 집락화를 시작합니다.
일부 박테리아는 호흡기 등 상피 세포에 고정하는 필리(pili) 또는 섬유질(fimbriae)을 가지고 있습니다.
많은 병원성 박테리아는 부착 단백질인 표면 단백질을 발현하여 숙주 세포와의 부착을 강화합니다.
부착 후 병원체는 숙주 내에 자리 잡기 시작합니다.
특정 박테리아는 바이오필름을 형성하여 면역 공격과 치료 저항성으로부터 보호합니다.
정착 후, 특정 병원체는 히알루로니다제나 코응고효소와 같은 효소를 생성하여 감염 중 조직 침범을 촉진합니다.
특정 병원체는 항원 구조를 가리고 면역 세포의 식을 막기 위해 캡슐을 형성합니다.
또는 항원 변이를 통해 특정 병원체가 표면 단백질을 변형해 면역을 회피하고 집락화를 확장할 수 있습니다.
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Q1: How do bacteria initially attach to host cells during colonization?
Bacteria initiate colonization by using specialized structures like pili or fimbriae to anchor to epithelial cells in areas such as the respiratory tract. Many pathogenic bacteria also express surface proteins called adhesins, which strengthen attachment by recognizing and binding to extracellular matrix components or cell surface molecules on host cells.
Q2: What is the difference between colonization and infection?
Colonization occurs when pathogens attach to and establish themselves within host tissues without immediately causing disease. Infection develops only when colonization leads to tissue damage or triggers a host inflammatory response. Many prokaryotic and eukaryotic pathogens can colonize tissues for extended periods before progressing to active infection.
Q3: How do biofilms protect bacteria from immune attacks?
Biofilms are structured communities of bacteria encased in a self-produced extracellular matrix that provides enhanced protection against phagocytosis and antimicrobial agents. This protective structure significantly increases pathogen persistence within the host. Quorum sensing, a form of bacterial communication via signaling molecules, regulates biofilm formation and virulence factor expression.
Q4: What enzymes do pathogens produce to facilitate tissue invasion?
Pathogens produce enzymes such as hyaluronidase and coagulase to facilitate tissue invasion. Hyaluronidase breaks down hyaluronic acid in connective tissues, aiding tissue penetration, while coagulase induces fibrin clot formation that may shield bacteria from immune cells. These enzymatic secretions help pathogens establish deeper infections within host tissues.
Q5: How do bacterial capsules help pathogens evade the immune system?
Bacterial capsules are composed of polysaccharides that mask antigenic cell surface components, preventing recognition and phagocytosis by immune cells. This immune evasion strategy allows pathogens to avoid detection and elimination. Capsules represent one of several mechanisms pathogens use to establish persistent infections and resist host defenses.
Q6: What is antigenic variation and how does it extend colonization?
Antigenic variation is a mechanism in which pathogens alter surface protein structures to escape recognition by host antibodies. This strategy allows prolonged colonization and chronic or relapsing infections. Pathogens such as Neisseria gonorrhoeae and Trypanosoma brucei are well known for using antigenic variation to evade immune detection and maintain persistent infections.
Q7: How do intracellular pathogens like Listeria monocytogenes avoid immune surveillance?
Some bacteria adopt an intracellular lifestyle to circumvent immune surveillance by invading host cells and exploiting the host cytoskeleton. These pathogens use actin-based motility structures, commonly termed actin rockets, to propel themselves and enable direct cell-to-cell transmission. This intracellular movement minimizes exposure to extracellular immune defenses and represents a key determinant of bacterial pathogenicity and virulence.